What it means
Battery cluster cell undertemperature alarm (level 1)
Cause: Cell minimum temperature < 5°C.
How to fix it
- Send faults externally.
- Recovers when Temp_min > 10°C.
Source: FLS-ES232LC-S.pdf
Felicity ESS error 0x1021
Battery cluster cell undertemperature alarm (level 1)
Warning — a protection warning — the ESS unit keeps running, but deal with the cause before it escalates.
Frequently asked questions
- What does error 0x1021 mean on a Felicity ESS?
- 0x1021 means: Battery cluster cell undertemperature alarm (level 1). Cell minimum temperature < 5°C.
- Is error 0x1021 a fault or a warning?
- 0x1021 is a warning: the unit keeps running. Fix the underlying condition before it escalates.
- How do I clear or fix error 0x1021?
- Send faults externally. Recovers when Temp_min > 10°C.
Related error codes
Other codes on the FLS-ES232LC-S
- 0x10A1WarningCell voltage accumulation overvoltage alarm in battery cluster (level 1).
- 0x10A2FaultCell voltage accumulation overvoltage alarm in battery cluster (level 2).
- 0x10A3CriticalCell voltage accumulation overvoltage alarm in battery cluster (level 3).
- 0x10B1WarningCell voltage accumulation undervoltage alarm in battery cluster (level 1).
- 0x10B2FaultCell voltage accumulation undervoltage alarm in battery cluster (level 2).
- 0x10B3CriticalCell voltage accumulation undervoltage alarm in battery cluster (level 3).
Prefer the full written guide? Read the complete Felicity inverter error-code guide
Compiled from official Felicity user manuals. Always consult your device manual and a qualified technician before performing repairs.